RAPIDMOC Data Quality Report

The pressure and pressure residual data are of good quality.

The temperature data in all series have step-like features. This is thought to be due to the magnitude of the changes in temperature being approximately equal to the resolution of the instrument. Therefore, the temperature data should be used with caution.

Processing Log

RAPIDMOC/MOCHA Sea-Bird BPR data processing document

This document outlines the procedures undertaken to process and quality assure the BPR data collected under the RAPIDMOC and MOCHA projects.

Originator's processing

The raw data are downloaded from the instrument and converted to ASCII format. All processing is performed in Matlab.

Processing

Processing steps which are undertaken include

calculation and removal of a post recovery clock offset.

calculation of a pressure offset for atmospheric correction. However, this may not be applied. See the calibration coefficients documents for each series for more information.

calculation of an exponential-linear or pure linear pressure fit. This is stored with pressure and temperature data in a file with a .use extension.

filtering of the pressure data using a 2 day low pass filter to remove the diurnal and semi-diurnal tides.

interpolating the temperature and de-trended, filtered pressure data onto a 12 hour time grid. This is stored in a file with a .seagauge extension.

calculation of a harmonic fit of the fortnightly and monthly tides. Also stored in the .seagauge extension file.

Quality control

All variables in specified time intervals can be set to dummy values if the data are suspicious. Any data deemed as suspicious, i.e. a spike, are removed.

BODC processing

Data are received after quality checks have been made and calibrations have been applied by the originator. The data files are submitted in ASCII format as two files per instrument.

Once the submitted data files are safely archived, the data undergo reformatting and banking procedures:

The data are transferred into a common format, a NetCDF subset.

The pressure and temperature channels from the .use file are combined with the pressure residual channel (de-trended and 2-day low pass filtered) from the .seagauge file into a single file. In addition a de-trended, unfiltered pressure (measured variable) series is derived by subtracting the calculated trend from the observed pressure, which were supplied in the originator's files with an extension of .use.

Rapid Climate Change (RAPID) Programme

Rapid Climate Change (RAPID) is a £20 million, six-year (2001-2007) programme of the Natural Environment Research Council (NERC). The programme aims to improve our ability to quantify the probability and magnitude of future rapid change in climate, with a main (but not exclusive) focus on the role of the Atlantic Ocean's Thermohaline Circulation.

Scientific Objectives

To establish a pre-operational prototype system to continuously observe the strength and structure of the Atlantic Meridional Overturning Circulation (MOC).

To support long-term direct observations of water, heat, salt, and ice transports at critical locations in the northern North Atlantic, to quantify the atmospheric and other (e.g. river run-off, ice sheet discharge) forcing of these transports, and to perform process studies of ocean mixing at northern high latitudes.

To construct well-calibrated and time-resolved palaeo data records of past climate change, including error estimates, with a particular emphasis on the quantification of the timing and magnitude of rapid change at annual to centennial time-scales.

To develop and use high-resolution physical models to synthesise observational data.

To apply a hierarchy of modelling approaches to understand the processes that connect changes in ocean convection and its atmospheric forcing to the large-scale transports relevant to the modulation of climate.

To understand, using model experimentation and data (palaeo and present day), the atmosphere's response to large changes in Atlantic northward heat transport, in particular changes in storm tracks, storm frequency, storm strengths, and energy and moisture transports.

To use both instrumental and palaeo data for the quantitative testing of models' abilities to reproduce climate variability and rapid changes on annual to centennial time-scales. To explore the extent to which these data can provide direct information about the thermohaline circulation (THC) and other possible rapid changes in the climate system and their impact.

To quantify the probability and magnitude of potential future rapid climate change, and the uncertainties in these estimates.

Projects

Overall 38 projects have been funded by the RAPID programme. These include 4 which focus on Monitoring the Meridional Overturning Circulation (MOC), and 5 international projects jointly funded by the Netherlands Organisation for Scientific Research, the Research Council of Norway and NERC.

The RAPID effort to design a system to continuously monitor the strength and structure of the North Atlantic Meridional Overturning Circulation is being matched by comparative funding from the US National Science Foundation (NSF) for collaborative projects reviewed jointly with the NERC proposals. Three projects were funded by NSF.

A proportion of RAPID funding as been made available for Small and Medium Sized Enterprises (SMEs) as part of NERC's Small Business Research Initiative (SBRI). The SBRI aims to stimulate innovation in the economy by encouraging more high-tech small firms to start up or to develop new research capacities. As a result 4 projects have been funded.

Monitoring the Meridional Overturning Circulation at 26.5N (RAPIDMOC)

Scientific Rationale

There is a northward transport of heat throughout the Atlantic, reaching a maximum of 1.3PW (25% of the global heat flux) around 24.5°N. The heat transport is a balance of the northward flux of a warm Gulf Stream, and a southward flux of cooler thermocline and cold North Atlantic Deep Water that is known as the meridional overturning circulation (MOC). As a consequence of the MOC northwest Europe enjoys a mild climate for its latitude: however abrupt rearrangement of the Atlantic Circulation has been shown in climate models and in palaeoclimate records to be responsible for a cooling of European climate of between 5-10°C. A principal objective of the RAPID programme is the development of a pre-operational prototype system that will continuously observe the strength and structure of the MOC. An initiative has been formed to fulfill this objective and consists of three interlinked projects:

A mooring array spanning the Atlantic at 26.5°N to measure the southward branch of the MOC (Hirschi et al., 2003 and Baehr et al., 2004).

Additional moorings deployed in the western boundary along 26.5°N (by Prof. Bill Johns, University of Miami) to resolve transport in the Deep Western Boundary Current (Bryden et al., 2005). These moorings allow surface-to-bottom density profiles along the western boundary, Mid-Atlantic Ridge, and eastern boundary to be observed. As a result, the transatlantic pressure gradient can be continuously measured.

Monitoring of the northward branch of the MOC using submarine telephone cables in the Florida Straits (Baringer et al., 2001) led by Dr Molly Baringer (NOAA/AOML/PHOD).

The entire monitoring array system created by the three projects will be recovered and redeployed annually until 2008 under RAPID funding. From 2008 until 2014 the array will continue to be serviced annually under RAPID-WATCH funding.

The array will be focussed on three regions, the Eastern Boundary (EB), the Mid Atlantic Ridge (MAR) and the Western Boundary (WB). The geographical extent of these regions are as follows:

Eastern Boundary (EB) array defined as a box with the south-east corner at 23.5°N, 25.5°W and the north-west corner at 29.0°N, 12.0°W

Mid Atlantic Ridge (MAR) array defined as a box with the south-east corner at 23.0°N, 52.1°W and the north-west corner at 26.5°N, 40.0°W

Western Boundary (WB) array defined as a box with the south-east corner at 26.0°N, 77.5°W and the north-west corner at 27.5°N, 69.5°W

Fixed Station Information

Station Name

Western Boundary Array

Category

Offshore area

Latitude

26° 37.50' N

Longitude

73° 37.50' W

Water depth below MSL

RAPIDMOC/MOCHA Western Boundary (WB) Array

The Western Boundary Array defines a box in which moorings were deployed at the western side of the North Atlantic as part of the RAPIDMOC project and the collaborative project Meridional Overturning Circulation and Heatflux Array (MOCHA). The box region has latitudinal limits of 26° N to 27.5° N and longitudinal limits of 69.5° W to 77.5° W. Moorings have occupied this region since 2004 and are typically deployed for 6 to 18 months.

Moored data summary

Year

Cruise ID

Number of moorings

Data types (number of instruments)

2004

D278

9 (6 RAPIDMOC, 3 MOCHA)

ADCP (2), BPR (8), CM (29), MCTD (52), MMP (1)

2005

KN182_2

11 (6 RAPIDMOC, 5 MOCHA)

ADCP (2), BPR (6), CM (27), MCTD (56)

2006

RB06-02, SJ14-06

11 (6 RAPIDMOC, 5 MOCHA)

ADCP (1), BPR (3), CM (22), IES (7), MCTD (60)

2007

RB07-01

7 (7 RAPIDMOC)

ADCP (1), BPR (4), CM (16), MCTD (47)

2008

SJ08-03

11 (8 RAPIDMOC, 3 MOCHA)

ADCP (2), BPR (3), CM (40), MCTD (80)

2009

RB0901, D344, D345

16 (11 RAPIDMOC, 5 MOCHA)

ADCP (2), BPR (5), CM (39), MCTD (91), DVS (1)

2010

OC459-1, RB1009

9 (8 RAPIDMOC, 1 MOCHA)

ADCP (1), BPR (7), CM (23), MCTD (54)

2011

KN200-4

7 (7 RAPIDMOC, 6 MOCHA)

ADCP (2), BPR (7), CM (43), MCTD (86), DVS (1), IES (1)

2012

RB1201, EN517, D382

24 (19 RAPIDMOC, 5 MOCHA)

ADCP (3), BPR (19), CM (74), MCTD (130), IES(1)

2014

JC103

24 (9 RAPIDMOC)

BPR (8), CM (22), MCTD (36)

Cruise data summary

During the cruises to service the moored array, a variety of data types are collected. The table below is a summary of these data. The number of CTD profiles performed on these cruises within the box region defined above is also included. Trans-Atlantic hydrographic CTD sections have also been performed since 2004 and are included in the table.